bennett



(Ho Model.) J F BENNETT 2 s hgets-dheet 1.. BLAST FURNACE STOVE.

No. 303,208. Patented Aug. 5, 1884.

k U \Msxm & '%Mw\wt UNITED STATES tries,

JOHN F. nnnnnrr, or PITTSBURG, PnnivsYLvAril-n BLAST-FU RNACE STOVF SPECIFICATION forming part of Letters Patent No. 303,208, dated August '5, 1884.

Application filed September 2-1, 883. (No model.)

To 0555107210712, it may concern:

Be it known that I, JOHN FRANCIS BEN- meter, of Pittsburg, inv the county of Allegheny and State of Pennsylvania, have in- 5 vented. certain new and useful Improvements in Blast-Furnace Stoves; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and to the letof approximately all their heating-power by causing their successive contact with air-pipes 5 in the stove and with a boiler to generate steam;

fourth, to attainthese objects with the maximum simplicity of construction. I attain these objects by the means illustratediu the accompanying drawings, in which 0 Figure I represents an elevation of the plant, the view being taken from behind thechimncy. Fig. 2 is a longitudinal section of the same, partially broken to show construction.

Similar letters referto corresponding parts- 5 in each'view.-

A represents a duct admitting the hot gases froma furnace or other source to a stove.

A is a valve-boxin which a slide-valve reciprocates, thereby conveying atmospheric air to meet the hot gases, insuring combustion in the chamber J.-

- B is a passage leading said gases, deprived partially of their'heat by contact with the pipes and the walls of the furnace, to the chimney H, in the bottom of which is located a steamgenerator, to deprive the gases of any heatingpcw'er remaining-in them. It is obvious, however, that the boiler might be placed elsewhere with equal eliiciency, provided its location is somewhere between the exit of the hot gases from the stove and the chimney.

tors of reference marked thereon, which form.

C is the entrance of an iron pipe conducting cold or atmospheric air to the stove, and D is the exit for this air, heated by traversing the iron pipes E E E E E E and their connecti.ng bo es F Fl F F!!! FI/I/ FM!!! I represents the outer walls of the furnace, which I so construct that the roof gradually increases in height as it approaches a perpendicular to the inlet A. I regulate this vertical enlargement by the increasing height of the 'iron pipes E E E" E E, preserving in each case the same distance between the top of the iron pipes and the roof wall of the furnace. The iron pipes E E, being of the same altitude, are covered by portions of the roof in the same horizontal plane; but each of the other pipes is covered by portions thereof in different planes.

hen I use this stove singly, in connection with blast-furnaccs, I make the pipe 0 of a diameter equal, approximately, one-half of that of the blower-exit; when two are needed, about one-fourth; and for three, abdut onesixth. I construct each of the boxes 1* F F F F F"" of an area equal to that of the pipe 0. From the first box F the air is forced by the blower into the first pipe E, and then successively into the second box F, second pipe E, box F, pipe E, box F, pipe E, box F', pipe E', box F, pipe E, box F and out through iron pipe I). I make the en-' trances and exits of the iron pipes E E E E E' E greater than the bodies of the respective pipes by approximately fifty percent. The slope of this increase on the two ends of each pipe extends for about two diameters of the pipe. I prefer to make these entrances and exits oblong with flat sides, about sixteen by four inches, rather than round of a diameter of eight and five-tenths inches, these two havingIt-he same area. Near the top of the pipes E E E E E E I gradually increase the diameter until at the crown the area is fifty per cent. greater than that of the body of the pipe. Usually I place fortyeight pipes in each stove, and six boxes. PipesE E, I generally give an altitude of twelve feet, and leave a space-of about six inches between the outer surface of the top of thepipe and the inner surface of the furnaceroof wall. The pipes E E E E are then made to have respeetive heights of fourteen, sixteen, eighteen, and twenty feet, and an equal space between their crowns and the roof of the furnace. The inlet and outlet air-pipes'O and D are made of areas equal to the box F. The inlet -pipe A terminates in a combustionchamber, J, combustion being assisted by the atmospheric airintrodu c'ed by the slide-valve A. The combustion-chamber extends as far as the inner perpendicular of ,the box F, and conducts the hot gases, products of combustion from the furnace-gases, and air from the inlet A to passages K K K, between the boxes, by which a continuously-ascending passage is provided for the gases, after which the gases descending between the first and second boxes F F arrive at the outlet B, whence they are conducted under a boiler, G, to utilize any heating-power remaining therein, and then discharged to the atmosphere by the shaft H. WVhen the shaft rises one hundred and fifty feet above the surface of the ground, the boiler G may be constructed with a height of about twenty feet. The boiler, though concentric with the shaft, leaves a space of about four inches between its outer surface and the inner wall of the shaft, providing ample passage for the gases. The boiler may have suitablc safetyvalves, gages, water supply and steam pipes, and the usual connection with an engine. The chimney is so placed as to carry off all the waste gases from the blast-furnace plant of which the stove or stoves form a part.

Iron-pipe stoves as heretofore constructed receive the blast-furnace gases (in best practice) at an average temperature of 400 Fahrenheit, mixed with proper proportions of air,

having an average yearly temperature of Fahrenheit, admitted through suitable slidevalves. The gases and air combine and expand in a combustiorrehamber. The blastfurnace gases are chiefly carbonic oxide, with accompanying proportion of nitrogen, the same proportion as exists in the atmosphere. If they were entirely of this composition, and of 0 Fahrenheit, and combined with their equivalentofatmosphericair, ad mitted through slide-valves, also at 0 Fahrenheit, the products of combustion would be five times the initial volume, and be of a temperature of 2,700 Fahrenheit, (carbonic-acid gas and nitrogen.) In practice, however, the blast-furnace gases contain about fourteen per cent. of carbonic acid gas and its accompanying nitrogen, also a percentage of vapor of water, varying according to the freedom from moisture of the stock charged into the furnace and the dry or humid condition of the atmospheric air blown into the furnace; also, the atmospheric air with which the blast-furnace gases combine in the chamber beneath the iron pipes contains more or less moisture. These noncombustible gases and vapors have to be raised to the average resulting temperature, and in being raised decrease the average intensity of the heat of the resulting products of combustion, although the volume of gases is increased.

1 Blast-furnace gases entering the stove at 400 Fahrenheit, and the atmospheric air with which they combine entering at 50 Fahrenheit, there being added thereto the heat of the combination, (2,700 Fahrenheit,) giving an average temperature of 2,925 Fahrenheit, if free from foreign substances; but in good practice hitherto the resulting heat obtained is about 2,000 Fahrenheit. As the products of combustion conveying this heat of 2,000 Fahrenheit pass from the chamber up through the stove, they heat the iron pipes, and then pass out of the stove through little chimneys K K in its roof at a temperature of about 1,000 Fahrenheit. The atmospheric air entering at the blower end of the first row of pipes at a temperature of 50 Fahrenheit in passing through the series of pipes is gradually increased in temperature until it passes out aha temperature in degree according to the aggregate length of the pipe, the height of the walls, and the velocity of the current of air passing through the pipes. For example, an iron-pipe stove containing eight rows of pipes at an average double length of sixteen and six-tenths feet, or, total, two hundred and sixty feet-eight pipes in each rowthe area of each pipe being sixty and fifty-six hundredths square inches,with a given velocity of air, gives a temperature to the air passing out of 1,000 Fahrenheit,which is the best average practice yet attained. There is also the disadvantage of a great velocity of the hot current burning the first rows of pipes, because striking the rows of pipes nearest the entrance of and velocity than the rows of pipes nearest the blower. This isto some extent overcome in practice with constant watching by closing a damper immediately above the top of the little chimney between the rows of pipes first reached. In spite of all care,the pipes do frequently burn and crack, and have to be replaced. In the new stove the burning gases pass in at the same'temperature and deliver the greatest intensity of heat to the rows of pipes nearest their entrance, but becoming cooler as their heat is abstracted by the pipes and air passing through the pipes, and consequently heavier, and being pushed out of the way by the velocity and pressure of the continuously-rising hot gases, and being continually drawn away by the vdraft of the hot chimney, they gradually course toward the cooler end of the stove and are drawn out at an average temperature of about 7 00 Fahrenheit. The result is that an additional temperature of 300 Fahrenheit is given to the hot-air blast. In the best practice the old iron-pipe stove gave an average temperature of 1,000 Fahrenheit to the blast,

average temperature of 1,300 Fahrenheit. As practically 100 Fahrenheit is equal to three per cent. of the best coke fuel,ora greater per cent. of inferior fuel, therefore 300 Fahrenheit is equal to nine per cent. of fuel saved. In addition the blast-furnace produces nine or but the new iron-pipe stove will give it an the burning gasesflvith greater degree of heat 7 about ten per cent. more pig-iron. Again,

the gases passing out of the stove at 100 Fahrenheit instead of being delivered into the air are made to pass under the boilers and raise steam enough to drive the engines for the blower and the whole plant, passing finally out of the chimney at 850 Fahrenheit. Heat: ing-gases under boilers must pass off at 350 Fahrenheit, because that is the temperature of the water in the boilers at a pressure of one hundred pounds to the square inch. There being a difference in temperature of from 300 to 400 Fahrenheit between the iron outside wall of the pipes next to the burning gases and the iron inside of the pipes next to the heat ing-air, the air cannot attain the same temperature as the gases that heat it. In practice there is alimit to the temperature of iron pipes conveying heated air. In the old iron-pipe stove it has been limited to heating the blast to 1,000 Fahrenheit at its outlet, the outlet rows of pipes being excessively and dangerously heated by the intensity and velocity of the hot current; but it is of record that an iron-pipe stove with its pipes almost White hot was 'kept during the entire night at a temperature of 1,900 Fahrenheit without injury to the pipes. The rounded entrances to the iron pipes obviate all friction, excepting that of the air against the walls, which is This is a great saving of enginepower. For example, the blower of one of the furnaces now largely in use delivers a blast of cold air into three hot stoves, each stove containing sixty-four pipes, (eight rows of eight pipes each,) each pipe being sixty square inches in area, or twenty four currents of one thousand four hundred and forty square inches, eachat a pressure of three or four pounds to the square inch in the cold-air main pipe,

which air, being heated while passing through the hot stoves to 1,000 Fahrenheit, and expanded to twice its initial volume enters the hot-air main pipe at a pressure of two and a quarterpounds to the square inch, thus hav ing lost nearly thirty per cent.of the pressure of the blower by the obstruction to the air While passing through the eight square-edged entrances and exits and the eight restricted curved crowns of the pipes. Thus it will be seen that estimating the loss at one and aquarter per cent. for each diminution of area in two hundred and sixty feet length of pipe, even at this low pressure, amounts to a heavy loss in volume.

Having thus fully described my invention, what I claim, and wish to secure by Letters Patent of the United States, is-

1. The combination, with a hot-blast stove having its roof formed in steps, of a series of hot-air pipes of varying heights and arranged in relation to said steps, substantially in the manner and for the purpose specified.

2. A stove, Lhaving its roof formed in steps, in combination with the iron pipes E E E E E E, of fixedly differing altitudes, boxes F F F F{ F F, blast-furnace gas inlet A, cold-air inlet A, combustion-chamber J and outlet B, cold-air inlet 0, and outlet D, inten vening passages K K K, the chimney H, and boiler G, the whole in the relation and for the purpose herein described and shown.

In testimony that I claim the foregoing as my own I aflix my signature in presence of two witnesses.

JOHN F. BENNETT.

Witnesses:

M. E. HAnnrsoN, ALEX. RANDOL. 

